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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10.     public static int getNumberSameAsIndex(int[] numbers) {
  11.         if(numbers == null || numbers.length == 0) {
  12.             return -1;
  13.         }
  14.  
  15.         int left = 0;
  16.         int right = numbers.length - 1;
  17.         while(left <= right) {
  18.             int middle = left + ((right - left) >>> 1);
  19.             if(numbers[middle] == middle) {
  20.                 return middle;
  21.             }
  22.  
  23.             if(numbers[middle] > middle) {
  24.                 right = middle - 1;
  25.             }
  26.             else {
  27.                 left = middle + 1;
  28.             }
  29.         }
  30.  
  31.         return -1;
  32.     }
  33.  
  34.     // ----------------------- TEST CODE -----------------------
  35.     private static void test(String testName, int[] numbers, int expected) {
  36.         if(getNumberSameAsIndex(numbers) == expected) {
  37.             System.out.println(testName + " passed.");
  38.         }
  39.         else {
  40.             System.out.println(testName + " FAILED.");
  41.         }
  42.     }
  43.  
  44.     private static void test1() {
  45.         int[] numbers = {-3, -1, 1, 3, 5};
  46.         int expected = 3;
  47.         test("test1", numbers, expected);
  48.     }
  49.  
  50.     private static void test2() {
  51.         int[] numbers = {0, 1, 3, 5, 6};
  52.         int expected = 0;
  53.         test("test2", numbers, expected);
  54.     }
  55.  
  56.     private static void test3() {
  57.         int[] numbers = {-1, 0, 1, 2, 4};
  58.         int expected = 4;
  59.         test("test3", numbers, expected);
  60.     }
  61.  
  62.     private static void test4() {
  63.         int[] numbers = {-1, 0, 1, 2, 5};
  64.         int expected = -1;
  65.         test("test4", numbers, expected);
  66.     }
  67.  
  68.     private static void test5() {
  69.         int[] numbers = {0};
  70.         int expected = 0;
  71.         test("test5", numbers, expected);
  72.     }
  73.  
  74.     private static void test6() {
  75.         int[] numbers = {10};
  76.         int expected = -1;
  77.         test("test6", numbers, expected);
  78.     }
  79.  
  80.     public static void main (String[] args) throws java.lang.Exception {
  81.         test1();
  82.         test2();
  83.         test3();
  84.         test4();
  85.         test5();
  86.         test6();
  87.     }
  88. }
Success #stdin #stdout 0.08s 380160KB
comments (?)
stdin 
Standard input is empty
stdout 
test1 passed.
test2 passed.
test3 passed.
test4 passed.
test5 passed.
test6 passed.
https://ideone.com/ZSd9kG
Integer identical to index
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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